There's usually two types of trademarking.
One's the usual 'We're going to make a release' trademarking which you sort of have to do to sell a product, at least if you don't want to have to fight off people in a court of law.
Then there's what's known as defensive trademarking.
This is when you trademark something to basically tell any other parties that may encroach on the IP in a country to 'back off', as you are apparently intending to release something (and it works on a first come, first serve basis, but there are of course costs and paperwork in doing so.)
Depending on the region, you have to let go of the trademark after a certain amount of time, if you fail to do anything with it, but the period is fairly long (due to you know, registering a trademark, and you know, developing an IP, for example) and it's mostly the renewal costs that get you if you intend to do it for fun.
This is normally used for IP defensive reasons, and it's pretty common in business.
It's also used as due cause for a C&D. If you're working on the IP commercially, and someone is infringing on your work (fan translation, for instance), having the trademark there as proof of deployment usually gives a lot of legal clout, if the C&D is ever contested in a court of law.